Tendril-less regulates tendril formation in pea leaves
Hofer, J and Turner, L and Moreau, C and Ambrose, M and Isaac, P and Butcher, S and Weller, JL and Dupin, A and Dalmais, M and Le Signor, C and Bendahmane, A and Ellis, N, Tendril-less regulates tendril formation in pea leaves, Plant Cell, 21, (2) pp. 420-428. ISSN 1040-4651 (2009) [Refereed Article]
Tendrils are contact-sensitive, filamentous organs that permit climbing plants to tether to their taller neighbors. Tendrilled
legume species are grown as field crops, where the tendrils contribute to the physical support of the crop prior to harvest.
The homeotic tendril-less (tl) mutation in garden pea (Pisum sativum), identified almost a century ago, transforms tendrils
into leaflets. In this study, we used a systematic marker screen of fast neutron–generated tl deletion mutants to identify Tl
as a Class I homeodomain leucine zipper (HDZIP) transcription factor. We confirmed the tendril-less phenotype as loss of
function by targeting induced local lesions in genomes (TILLING) in garden pea and by analysis of the tendril-less phenotype
of the t mutant in sweet pea (Lathyrus odoratus). The conversion of tendrils into leaflets in both mutants demonstrates that
the pea tendril is a modified leaflet, inhibited from completing laminar development by Tl. We provide evidence to show that
lamina inhibition requires Unifoliata/LEAFY-mediated Tl expression in organs emerging in the distal region of the leaf
primordium. Phylogenetic analyses show that Tl is an unusual Class I HDZIP protein and that tendrils evolved either once or
twice in Papilionoid legumes. We suggest that tendrils arose in the Fabeae clade of Papilionoid legumes through acquisition
of the Tl gene.